Echinothrix diadema (Linnaeus, 1758)

Filander, Zoleka, Samyn, Yves & Griffiths, Charles, 2019, Four notable additions to the South African echinoid fauna (Echinodermata, Echinoidea), ZooKeys 831, pp. 71-80 : 72-74

Echinothrix diadema (Linnaeus, 1758) Fig. 1C, D

Garelia cincta : Agassiz 1863: 18-19.

Echinothrix diadema : Mortensen 1940: 290-295, pl. XLIII, figs 1-2, pl. XLV, figs 1-8, pl. XLVI, figs 2-4, pl. XLVII, figs 4, 6-7, pl. XLVIII, fig. 4, pl. LXXI, figs 1, 3 [synonym and description]; Clark and Rowe 1971: 153, fig. 64a [description and distribution]; Samyn and Vanden Berghe 2000: 11 [distribution].

Identification.

Test large sized (test diameter = 120 mm). Ambulacra not bulging, with one primary tubercle per three pore-pairs. Interambulacra with distinctively large, perforated, and crenulated primary tubercles, where each plate is surrounded by six smaller tubercles. Areoles slightly deepened. Apical system with insert plates, where gonopores are positioned distally on genital plates. Spines banded, long, and needle-like, with a ridged surface. Denuded test creamy white and reported by Samyn and Vanden Berghe (2000) to be sometimes reddish.

Material examined.

RMCA.2561: one specimen collected from the intertidal zone of Isipingo Beach in August 1999; RMCA.2568: one specimen collected by SCUBA diving off 2-Mile Reef in August 1999, at 15 m. All were complete specimens which were fixed and originally preserved in 90-70% ethanol. At present they are preserved dry.

Habitat.

Littoral and reef habitats.

Global distribution.

Indo-Pacific: Paumotu, Tahiti, Hawaii to Japan, north Australia; to Madagascar, East Africa to Red Sea ( Mortensen 1940; Clark and Rowe 1971; Samyn and Vanden Berghe 2000).

South African distribution.

East coast of South Africa, south of Durban off Isipingo Beach (30.0036°S, 30.9425°E: approximate co-ordinates), and off 2-Mile Reef, Sodwana Bay (27.5129°S, 32.6862°E: approximate co-ordinates).

Remarks.

Echinothrix diadema closely resembles E. calamaris (Pallas, 1774), but differs in coloration, patterns of ambulacra, interambulacra, and apical plates. Echinothrix diadema is not reported to have a greenish denuded test, lacks a conspicuous naked interambulacral space, and the ambulacral tubercles increase in size at the ambitus; the apical plates have numerous tubercles ( Mortensen 1940).

The current record was not included in previous South African reviews ( Filander and Griffiths 2014; Filander and Griffiths 2017) because these publications were based on Iziko South African Museum samples and online accessible samples. Presented here is new material from the Royal Museum for Central Africa, which was not known by the authors at the time ( Filander and Griffiths 2014; Filander and Griffiths 2017).